In-line system and method for manufacturing liquid crystal display

ABSTRACT

An in-line system for fabricating a liquid crystal display includes a sealer coating unit for coating a sealer onto a first substrate with a plurality of liquid crystal display cell regions a liquid crystal injection unit for dropping a liquid crystal onto the first substrate coated with the sealer, and an assembly unit for assembling the first substrate with the second substrate, A sealer hardening unit hardens the sealer interposed between the first and the second substrate to thereby assemble the first and the second substrate with each other. A substrate cutting unit cuts the first and the second substrates along cutting lines through illuminating a laser beam along the cutting lines such that the first and the second substrates are severed into the liquid crystal display cell regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.10/762,436 filed on Jan. 22, 2004, which is a Continuation of U.S.patent application Ser. No. 10/108,045 filed on Mar. 27, 2002, now U.S.Pat. No, 6,710,843 and which claims priority to Korean PatentApplication No. 2001-34761 filed Jun. 19, 2001 in the KoreanIntellectual Property Office (KIPO), all of which are fully incorporatedherein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an in-line system for a liquid crystaldisplay, and a method of fabricating a liquid crystal display using thesame.

(b) Description of the Related Art

Generally, the fabrication of a liquid crystal display involvesprocesses of fabricating an array substrate where wiring line patternsand switching circuits (in the case of an active matrix type) are formedon a glass substrate, a liquid crystal display cell process wherealignment treatment, spacer formation and injection of a liquid crystalbetween the array substrate and an opposing substrate are made, and amodule process where attachment of driver ICs and mounting of abacklight are made.

A plurality of liquid crystal display cell regions are simultaneouslyformed at a mother glass in the array substrate fabrication process. Theplurality of liquid crystal display cell regions are severed from eachother to form separate display units through cutting in the liquidcrystal display cell process,

In the liquid crystal display cell process, a vacuum injection or a dropinjection may be made to fill the cells with liquid crystal.

With the vacuum injection, an alignment film is coated onto thesubstrates to align the liquid crystal molecules, and thensurface-treated. Spacers are formed at one of the substrates to maintainthe cell gap in a constant manner, and a sealer with a liquid crystalinlet hole is printed around the substrates. The substrates are thenaligned and assembled with each other through a hot press process with athermal-hardening sealer. After grooves are formed at the substrates pera panel unit through scribing, the substrates are severed from eachother through impact cutting. The respective panels are put into avacuum vessel such that the liquid crystal inlet hole of the sealer isdipped into a liquid crystal. In this way, the liquid crystal isinjected into the liquid crystal display cell. Finally, the liquidcrystal inlet hole is sealed such that the injected liquid crystal iscontained.

With the drop injection, an alignment film is coated onto thesubstrates, and then surface-treated. Spacers are formed at one of thesubstrates. After a sealer is formed around one of the substrates in theshape of a closed curve, a liquid crystal is dropped onto the substrate.The two substrates are aligned, and assembled with each other by way ofthe sealer. Finally, the sealer is hardened.

In the case of drop injection, as liquid crystal is contained within theliquid crystal display cell while being severed into unit cells throughscribing, the characteristic of the liquid crystal can deteriorate fromloss of alignment force of the alignment films and due to the impact tothe substrates, and this can result in poor display characteristics. Toprevent such a problem, the substrate severing may be completely made atthe groove formation process based on scribing by penetrating thecutting blade through the substrates. In this case, the stress appliedto the substrates at the cutting becomes increased Consequently, thepossibility of deteriorating the display characteristic of the liquidcrystal display cell is increased and production yield is decreased.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system and methodof fabricating a liquid crystal display which prevents deterioration ofthe display characteristic at the severing of the substrates into unitcells, thereby enhancing production yield.

An in-line system for fabricating a liquid crystal display is provided,the in-line system comprising a spacer dispersing unit for dispersingspacers onto at least one of first and second substrates with aplurality of liquid crystal display cell regions; a sealer coating unitfor coating a sealer onto the first substrate; a liquid crystalinjection unit for dropping liquid crystal onto the first substratecoated with the sealer; an assembly unit for assembling the firstsubstrate with the second substrate; a sealer hardening unit forhardening the sealer interposed between the first and the secondsubstrate to thereby join the first and the second substrate; and asubstrate cutting unit for cutting the first and the second substratesalong cutting lines through illuminating a laser beam along the cuttinglines such that the first and the second substrates are severed into theliquid crystal display cell regions,

Preferably, the substrate cutting unit comprises a laser for pre-heatingthe first and the second substrates along the cutting lines; a lasertransporter for fixing or transporting the laser; and a cooling agentspraying unit for cooling the pre-heated first and second substratesalong the cutting lines. The substrate cutting unit further comprises asubstrate transporter for fixing, rotating or transporting the first andthe second substrates. The cooling agent spraying unit is mounted on thelaser transporter.

According to a preferred embodiment of the present invention, the spacerdispersing unit, the sealer coating unit, the liquid crystal injectionunit, the assembly unit, the sealer hardening unit and the substratecutting unit are designed to be in-line, The in-line system furthercomprising first and second preliminary alignment units for aligning thefirst and the second substrates with each other before the assembling,and a heat treatment unit for heat-treating the liquid crystal.

A method is provided for fabricating a liquid crystal display, themethod comprising the steps of dispersing spacers onto at least one offirst and second substrates with a plurality of liquid crystal displaycell regions; coating a sealer onto the first substrate; dropping aliquid crystal onto the first substrate; assembling the first and thesecond substrates to join with each other; hardening the sealerinterposed between the first and the second substrates; and cutting thefirst and the second substrates along cutting lines using a laser suchthat the first and the second substrates are severed into a plurality ofliquid crystal display cell regions.

The step of cutting the first and the second substrates furthercomprises the steps of pre-heating the first and the second substratesalong the cutting lines through illuminating a laser beam along thecutting lines; cooling the first and the second substrates along thecutting lines through spraying a cooling agent along the cutting linesto thereby form a crack; and propagating the crack along the cuttinglines.

According to another preferred embodiment of the present invention anin-line system for fabricating a liquid crystal display comprises meansfor dispersing spacers between first and second substrates; means forjoining the first and second substrates to form a gap; means forinjecting liquid crystal onto the gap; and means for cutting the firstand the second substrates along cutting lines such that the first andthe second substrates are severed into the liquid crystal display cellregions.

The means for cutting comprises a laser for preheating the first and thesecond substrates along the cutting lines; a laser transporter forfixing or transporting the laser, and a cooling agent spraying unit forcooling the pre-heated first and second substrates along the cuttinglines.

The means for joining comprises a sealer coating unit and a sealerhardening unit the sealer coating unit for coating at least one of thefirst and second substrates with a sealer and the sealer hardening unitfor hardening the sealer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or the similar components, wherein:

FIG. 1 is a plan view of a mother panel for a liquid crystal displaywith a plurality of liquid crystal display cell regions according to apreferred embodiment of the present invention;

FIG. 2A is an amplified view of the IIa portion of FIG. 1;

FIG. 2B is a cross sectional view of the liquid crystal display takenalong the IIb-IIb′ line of FIG. 2;

FIG. 3 is a block diagram of an in-line system for fabricating theliquid crystal display shown in FIG. 1; and

FIG. 4 illustrates the process of cutting the substrates of the motherpanel shown in FIG. 1 using a substrate cutting unit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with referenceto the accompanying drawings.

FIG. 1 is a plan view of a mother panel for a liquid crystal displaywith a plurality of liquid crystal display cells according to apreferred embodiment of the present invention. FIG. 2A is an amplifiedview of the IIa portion of FIG. 1, and FIG. 28 is a cross sectional viewof the liquid crystal display taken along the IIb-IIb′ line of FIG. 2A.

As shown in FIG. 1, four liquid crystal display cell regions 10 a, 10 b,10 c and 10 d are formed at the mother panel 10. Cutting lines A and Bfor severing the mother panel 10 into several liquid crystal displayunit cells are indicated with dotted lines. The number of liquid crystaldisplay cell regions to be formed at one mother panel may be altereddepending upon the dimension of the mother panel and the liquid crystaldisplay cell.

A plurality of pixel regions 26 are formed at an array substrate 12 ofthe mother panel 10 in a matrix form while collectively defining adisplay area 24. A thin film transistor (not shown) is formed at eachpixel region 26. The thin film transistor is formed with a gateelectrode, a drain electrode, and a source electrode. The gate electrodeof the thin film transistor is connected to a gate line (not shown), andthe drain electrode thereof to a data line (not shown). The sourceelectrode of the thin film transistor is connected to a pixel electrode(not shown) formed at the pixel region 26. The data lines and the gatelines are connected to driving circuits (not shown) via terminals 14formed at the outer periphery of the array substrate 12.

A color filter substrate 16 faces the array substrate 12. The colorfilter substrate 16 is established to be smaller than the arraysubstrate 12 by the area of the terminals 14. A common electrode (notshown) and color filters of red R, green G and blue B (not shown) areformed at the color filter substrate 16. A display area black matrix 20and a peripheral area black matrix 22 are formed at the color filtersubstrate 16. The display area black matrix 20 partitions the pixelregions 26 within the display area to prevent leakage of light at theinter-pixel bordering area while absorbing light directed at the thinfilm transistors to prevent current leakage, The peripheral area blackmatrix 22 is provided to absorb light directed at the peripheral areaexternal to the display area.

The array substrate 12 and the color filter substrate 16 are assembledto face each other by way of an ultraviolet (UV) hardening sealer 18forming a gap there between. A liquid crystal 28 fills the gap betweenthe substrates 12 and 16. The liquid crystal is contained by theultraviolet hardening sealer 18. The sealer 18 is formed with a materialthat does not mix with the liquid crystal 28 to prevent the liquidcrystal 28 from being contaminated if it comes in contact with thesealer 18 before the sealer is hardened.

The substrates 12 and 16 are spaced apart from each other with apredetermined cell gap. The distance of the cell gap is kept constant byusing spacers of a predetermined size (not shown). However, if thedistribution density of the liquid crystal 28 is not uniform at theentire area of the substrates, the cell gap cannot be maintained in aconstant manner. In this case, the image displayed on the display screenof the display device is deteriorated. Therefore, the distributiondensity of the liquid crystal 28 should be controlled in a uniformmanner.

When the mother panel 10 is severed by cutting into the liquid crystaldisplay cell regions 10 a, 10 b, 10 c and 10 d along the cutting lines Aand B, the stress applied to the substrates 12 and 16 with the cuttingshould be minimized to prevent deformation of the liquid crystal displaycells and deterioration of the liquid crystal 28.

A method of fabricating the liquid crystal display using an in-linesystem will be now explained with reference to FIGS. 3 and 4.

FIG. 3 is a block diagram of the in-line system, and FIG. 4 illustratesa process of cutting the substrates using a substrate cutting unit.

As shown in FIG. 3, the in-line system includes a first load unit 100where one-sided substrates are classified and loaded, a spacerdispersing unit 200, a sealer coating unit 300, a liquid crystalinjection unit 400, and a first preliminary alignment unit 500. Thein-line system further includes a second load unit 600, a secondpreliminary alignment unit 700, an assembly unit 800, a sealer hardeningunit 900, a heat treatment unit 1000, a substrate cutting unit 1100, anda substrate unload unit 1200. The first load unit 100, the spacerdispersing unit 200, the sealer coating unit 300, the liquid crystalinjection unit 400, the first preliminary alignment unit 500, theassembly unit 800, the sealer hardening unit 900: the heat treatmentunit 1000, the substrate cutting unit 1100 and the unload unit 1200 aresequentially connected to each other by way of an in-line transporter(not shown) capable of transporting the substrates per the in-lineprocessing time unit, The second load unit 600 and the secondpreliminary alignment unit 700 are connected to the assembly unit 800 byway of another in-line transporter (not shown). In case the time periodof cutting the substrates 12 and 16 at the substrate cutting unit 1100differs from the in-line processing time period, a plurality ofsubstrate cutting units may be provided to ensure that the processing isin-line.

The bottom substrates 12 are classified, and loaded in the first loadunit 100. The spacer dispersing unit 200 disperses spacers onto thebottom substrate 12 to maintain the gap between the two substrates 12and 16 in a constant manner. The sealer coating unit 300 coats a sealer18 onto the bottom substrate 12 in the shape of a closed curve. Theliquid crystal injection unit 400 drops liquid crystal 28 into theliquid crystal display cell regions 10 a to 10 d defined by the sealer18 of the bottom substrate 12 using a liquid crystal injector (notshown). The liquid crystal injector may bear a shape of a syringecapable of dropping the liquid crystal 28 in a small scale, or a shapeof a sprayer with a nozzle capable of dropping the liquid crystal 28 ina full scale, The first preliminary alignment unit 500 preliminarilyaligns the bottom substrate 12 having the sealer 18 and the liquidcrystal 28 with the top substrate 16 before the assembling.

The top substrates 16 are classified, and loaded in the second load unit600. The second preliminary alignment unit 700 preliminarily aligns thetop substrate 16 with the bottom substrate 12 before the assembling. Theassembly unit 800 assembles the bottom and the top substrates 12 and 16opposite each other. Compression plates (not shown) are provided at theassembly unit 800 to apply pressure to the substrates 12 and 16. Thesealer hardening unit 900 hardens the sealer 18 interposed between thesubstrates 12 and 16. The heat treatment unit 1000 makes heat treatmentwith respect to the substrates 12 and 16 to align the liquid crystal 28in a stable manner. The substrate cutting unit 1100 illuminates a laserbeam onto the substrates 12 and 16 along the cutting lines A and B usinga cutter to thereby sever the substrates 12 and 16 into the liquidcrystal display unit cell regions 10 a to 10 d, The unload unit 1200unloads the severed substrates 12 and 16.

In case it is intended to form the spacers at the top substrate 16, thespacer dispersing unit 200 may be positioned between the second loadunit 600 and the second preliminary alignment unit 700,

The process of cutting the substrates using the substrate cutting unit1100 will now be explained with reference to FIG. 4.

As shown in FIG. 4, the substrate cutting unit 1100 includes a laser1101 for pre-heating the substrates 12 and 16 through illuminating alaser beam along the cutting lines A and B. A cooling agent sprayer 1103is installed at the rear of the laser 1101 to spray a cooling agent tothe laser-illuminated area such that a minute crack is made at thesubstrates 12 and 16 along the cutting lines A and B. The substratecutting unit 1100 further includes a laser transporter 1102 for fixingor transporting the laser 1101 and the cooling agent sprayer 1103. Thesubstrate cutting unit 1100 may further include a substrate transporterfor fixing, transporting or rotating the mother panel 10 with the bottomand top substrates 12 and 16 assembled by way of the sealer 18.

In the process of cutting the substrates 12 and 16, the laser 1101illuminates a laser beam onto the substrates 12 and 16 along the cuttinglines A and B, thereby pre-heating the substrates 12 and 16 up to apredetermined temperature. Thereafter, the cooling agent sprayer 1103sprays a cooling agent onto the pre-heated substrates 12 and 16 tothereby cool the pre-heated substrates 12 and 16 in a rapid manner.Thermal compression and thermal expansion are made at the substrates 12and 16 along the cutting lines A and B due to the heating and thecooling so that high thermal stress is applied to the substrates 12 and16. Consequently, a minute crack is formed at the substrates 12 and 16along the cutting lines A and B, and propagated along the cutting linesA and B as the laser beam illumination and the cooling agent sprayingare made. In this way the mother panel 10 is completely severed into theliquid crystal display unit cell regions 10 a to 10 d.

As described above, in the substrate cutting process, a laser beam isilluminated onto the substrates 12 and 16 in a non-contact manner toform a minute crack at the substrates 12 and 16. The minute crack ispropagated, thereby severing the substrates 12 and 16. In this process,the laser-based cutter does not contact the substrates 12 and 16 andstress from cutting substrates can be prevented. Furthermore, as theformation and propagation of the minute crack at the substrates 12 and16 are made without applying pressure to the substrates, deformation ofthe liquid crystal display cell or deterioration of the liquid crystaland the alignment films does not occur. Accordingly, the resultingdisplay device can involve the desired display characteristic in astable manner. In addition, as the liquid crystal display cell regions10 a to 10 d are designed without considering the cutting margin as withthe scribing process, the cell regions 10 a to 10 d can be enlarged insize.

In sum, a laser is introduced in the substrate cutting process whilepreventing the possible application of cutting stress to the substratesso that the liquid crystal or the alignment films are prevented frombeing deteriorated. Consequently, the display characteristic of theresulting liquid crystal display can be enhanced.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. An in-line system for fabricating a liquid crystal display, thein-line system comprising: a spacer dispersing unit for dispersingspacers onto at least one of first and second substrates with aplurality of liquid crystal display cell regions; a sealer coating unitfor coating a sealer onto the first substrate; a liquid crystalinjection unit for dropping liquid crystal onto the first substratecoated with the sealer; an assembly unit for assembling the firstsubstrate with the second substrate; a sealer hardening unit forhardening the sealer interposed between the first and the secondsubstrate to thereby join the first and the second substrate; and asubstrate cutting unit for cutting the first and the second substratesalong cutting lines through illuminating a laser beam along the cuttinglines such that the first and the second substrates are severed into theliquid crystal display cell regions.
 2. The in-line system of claim 1wherein the substrate cutting unit comprises: a laser for pre-heatingthe first and the second substrates along the cutting lines; a lasertransporter for fixing or transporting the laser; and a cooling agentspraying unit for cooling the pre-heated first and second substratesalong the cutting lines.
 3. The in-line system of claim 2 wherein thesubstrate cutting unit further comprises a substrate transporter forfixing, rotating or transporting the first and the second substrates. 4.The in-line system of claim 2, wherein the cooling agent spraying unitis mounted on the laser transporter.
 5. The in-line system of claim 1wherein the spacer dispersing unit, the sealer coating unit, the liquidcrystal injection unit, the assembly unit, the sealer hardening unit andthe substrate cutting unit are designed to be in-line.
 6. The in-linesystem of claim 1 further comprising first and second preliminaryalignment units for aligning the first and the second substrates witheach other before the assembling, and a heat treatment unit forheat-treating the liquid crystal.
 7. A method of fabricating a liquidcrystal display, the method comprising the steps of: dispersing spacersonto at least one of first and second substrates with a plurality ofliquid crystal display cell regions; coating a sealer onto the firstsubstrate; dropping a liquid crystal onto the first substrate;assembling the first and the second substrates to join with each other;hardening the sealer interposed between the first and the secondsubstrates; and cutting the first and the second substrates alongcutting lines using a laser such that the first and the secondsubstrates are severed into a plurality of liquid crystal display cellregions.
 8. The method of claim 7 wherein the step of cutting the firstand the second substrates further comprises the steps of: pre-heatingthe first and the second substrates along the cutting lines throughilluminating a laser beam along the cutting lines; cooling the first andthe second substrates along the cutting lines through spraying a coolingagent along the cutting lines to thereby form a crack; and propagatingthe crack along the cutting lines.
 9. An in-line system for fabricatinga liquid crystal display, the in-line system comprising: means fordispersing spacers between first and second substrates; means forjoining the first and second substrates to form a gap; means forinjecting liquid crystal onto the gap; and means for cutting the firstand the second substrates along cutting lines such that the first andthe second substrates are severed into the liquid crystal display cellregions.
 10. The in-line system of claim 9 wherein the means for cuttingcomprises: a laser for pre-heating the first and the second substratesalong the cutting tines; a laser transporter for fixing or transportingthe laser; and a cooling agent spraying unit for cooling the pre-heatedfirst and second substrates along the cutting lines.
 11. The in-linesystem of claim 9 wherein the means for joining comprises a sealercoating unit and a sealer hardening unit, the sealer coating unit forcoating at least one of the first and second substrates with a sealerand the sealer hardening unit for hardening the sealer.